A boiler is a device used to heat water or other fluids. The term can refer to a variety of different devices, including a HEATER, a KETTLE, a COPPER vessel, and a STOKER. A HEATER is a device that uses electricity, gas, or oil to generate heat. A KETTLE is a metal pot with a lid and a handle, used for boiling liquids. A COPPER vessel is a container made of COPPER, which is a metal alloy known for its heat-conducting properties. Finally, a STOKER is a device that burns coal or other fuel to produce heat.